/*  
 *  Copyright 2006 Paul Jack.
 *
 *  This file is part of the Dex compiler suite. 
 *  
 *  Dex is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the
 *  Free Software Foundation; either version 2 of the License, or (at your
 *  option) any later version.
 *  
 *  Dex is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
 *  Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */
package dex.misc;


import java.util.List;
import java.util.Map;


/**
 * A stack of maps.
 * 
 * (Used to implement variable scopes.)
 *
 * @param <K>  The type of the key in the map
 * @param <V>  The type of the value in the map
 */
public interface Scope<K,V> {


	/**
	 * Returns the layers as an unmodifiable list.
	 * The list goes from from most recently added layer to
	 * least recently added layer. 
	 * 
	 * @return
	 */
	List<Map<K,V>> layers();


	/**
	 * Adds a new layer.
	 */
	void add();


	/**
	 * Removes the most recent layer.
	 * 
	 * @throws IllegalStateException if only one layer is left
	 */
	void remove();


	/**
	 * Returns the most recently added layer.
	 * 
	 * @return  the most recently added layer
	 */
	Map<K,V> mostRecent();


}
